Salt plays a big part in making cakes. It's like a back drop so all the other flavors gets enhanced.. How about make a big one for everyone to eat using the regular recipe, then make a small one for yourself.

You must also remember that there is "hidden salt" (sodium) in almost EVERYTHING we eat. Check the label on things in your pantry. It seems to me it would be difficult indeed to make a totally "salt free" cake.